Trigger and sear mechanism



1951 F. w. SAMPSON ETAL 2,539,554

TRIGGER AND SEAR MECHANISM Original Filed May 1, 1944 2 Shets-Sheet 1 Fi, l 1 4 O o o o 6 I /v VENTOES FREDERICK VVLEAMF EUN,

EEDR'EE-J HYDE) ATToEA/E rs 1951 F. w. SAMPSON ETAL 2,539,554.

TRIGGER AND SEAR MECHANISM Original Filed May 1, 1944 V 2 Sheets-Sheet 2 ll 1 INVENfOS FREDERHIKW -Evxmpscm,

EEDREELIHY DE,

BY %,a. awzwx A T TOENEYS Patented Jan. 30, 1951 UNITED STATES PATENT OFFICE- TRIGGER AND SEAR- MECHANISM Frederick W; Sampson, Dayton,-Ohio, and George J. Hyde, Brooklyn; N. Y., assignors to General" Motors Corporation, a corporation of Delaware Original application May. 1,. 1944, Serial No. 533,566. Divided and this. application August 14, 1946, Serial No. 690,519

2 Claims. 1

Thisinvention relates to a trigger and sear sub-assembly used in small. arms of the type capable of sustained. automatic fire and commonly. referred'to as .a sub-machine gun ormachine pistol.v

An important object of the inventi'onis'to provideanintegratedsub-assembly that is susceptib1eofeconomical mass production and in'vvhich the principles oi reproduceability, and interchangeability'are carried to the highest degree.

This latterobjecth'as been attained by fabricatingfth'e. sub-assemblymainly from stamped parts having relatively. plain conformation thus resulting in the. elimination of tedious and'timeconsuming operations.

The present invention is intended for usewith guns of the character shown in application Serial No. 533,566, filed May 1,.1944,- and now abandoned, entitled AutomaticFirearmf of which this application is. a division.

Theexact nature ofthe invention as well. as

to:-F.'igure,2 butshowing the trigger andlsear sub.-

assembly in different stages in thecycleof op.- eration;

Figure 5 is anexploded view of the trigger and, sear sub-assembly; and

Figure 6 is a section through line 6--5.o.li'igure 1. showing the manner in which the pivots for the sub-assembly are detachably held in place.

The main frame of the weapon comprises two stamped halves joined bywelding or other convenient manner to form a substantially cylindrical receiver I having adependinghand grippertion 2 and depending side walls and-Miami a magazine housings The open. forward end of the receiver is completedby Welding or otherwise securingtherein an internally threaded barrel sleeve- 4. receiving a barrel 5..

Further .description of the weapon is contained imparent application Serial.No..533,566,- the present disclosure bein limited to the trig er and sear subsassembly which. will bBrIlOW described and, in so'far as applicable; thevarious-partswill be. identified by the same. reference numerals used in the parent application. r

The trigger and sear sub-assembly comprises a conveniently integrated mechanism, and as shown inFi'gure 5, it consists of a trigger 24 pivoted to one end of a link 25, a sear 26 pivotedto the other end. of the link 25, a spring 21 connected tosaid trigger 24 and link 25, a U-shapedclip ZB'and a pivot pin 30.

The trigger 24 is a substantially U-shapedsheet metal stamping having a pair of diverging arms.

The bottom forward portions of the diverging arms are integrally connected by a bridging portion to form a finger grip for-the trigger. Each of these arms is provided with a pair of pivot openings 24' and 25', Figures 2 and 5, and'portions 2 3", in the vicinity of each pivot opening E i, offset from the main oody of the arm. These ofiset portions 26 lie in planes parallel to the depending sides 42 and 43 of the receiver and bear against these sides'to prevent side play'of the trigger '24 in the receiver I.

The sear block 26 is provided with an upper pivot. aperture 2t to receive a pivot pin 33, a lower pin opening 25", a rearwardly extending step 29, and a shoulder 3!.

The link 25 is a channel-shaped sheet metal stamping provided at each end thereof with longitudinally extending arms provided at one end with openings 25 and at the opposite end with openings 26 The trigger 28 and the link 25 are also pro-- The trigger 24 is pivoted to the link 25 through a pair of rivet pins 25" and the link 25 to the sear 25. through a single headed pin se', to thereby form a unitary linkage system for a purpose to be described.

An elongated u-shap-ed'rod-lilieclip 28 is provided'with a rear arm 28' and-a forward arm'28".

As. shown in Figures 1 and 6, the main portion of the clip" 28 rests against the outside of the wall s2; One'of the arms 28' of the clipis insertedthrough aligned openings 2- in the'walls s2 and 4-3 andthe other arm. 23, through aligned openings 2" all for a purpose to. be explained. The clip 23 is locked" in place. by a housing; 44 which, as shown in Figures '1 and 6 eoversa'portion of element 28. The arm 23 is-the pivot for the trigger 24 and the arm 28'. a stop tolimit clockwise movement of the sear 25 by acting againstthe sear step 29. v

The receiver tiles in the lower portion thereof an openingwhich is defined by the rearwall of theinagazine housing 3, the depending receiver side Walls 'EZTandflSiand a. bottom Wall 43" on that portion of the receiver forming a housing for the trigger and sear sub-assembly. This opening is closed by a detachable sheet metal housing 44 which is provided at its front end with a tongue 45 engaging a slot 45' in the magazine housing 3, at its rear end with a tongue 45 for engaging a slot 46' in the trigger and sear sub-assembly housing and an aperture 4'! adapted to register with a similar aperture 48 in said wall 43'. A detachable trigger guard 49 formed of flexible material, is provided at one end with shoulders 49 and an arched tongue 50 which extends through the apertures 41 and 48 into engagement with the inner surface of the bottom receiver wall 43, and at its other end with a tongue 5! which is snapped into an aperture 5| in the hand grip 2 and thereby secures the housing 44 against the receiver walls 42, 43 and 43. As the side walls of the housing 44 overlap the depending receiver walls, it is provided with indentations 4| and 4|" to provide securing recesses for the forward ends of the clip 28 and the ends of the pivot pin 30, and thus serve as retainers for the elements 28 and 30 of the subassembly, the removal of the housing enabling these parts to be removed with great facility.

To install the trigger and sear sub-assembly, the parts are first connected together as shown in Figure 5. The receiver I is then turned upside down and the trigger and sear sub-assembly dropped through the bottom opening formed when the housing 44 is removed. The openings 24' are aligned with the openings 2' on the receiver sides 42 and 43 and the arm 28' of the clip 28 inserted through these pairs of aligned openings 2 and the other arm 28" of the clip 28 is placed through the openings 2" and extends across the receiver i to engage the rearwardly extending step 29 on the sear 26 to limit movement thereof. The sear 26 likewise is aligned, with its opening 26 to register with the openings 42' in the receiver walls 42 and 43, and the pin 30 inserted whereupon the shoulder 3| is impelled by the link and the spring 21 to extend in a position to engage the shoulder 32 on the bolt 10. To disassemble, the trigger guard 49 is forced out of aperture 5| and rotated out of apertures 47 and 48, the housing 44 removed and the pin 28 pulled away from the receiver and the sear pin 39 forced out of its openings. The gun is then turned upside down, tipped forwardly and then right side up so that the,trigger and sear sub-assembly will drop out of the bottom opening of the receiver.

To operate, the trigger 24 is pulled against the tension of the spring 21, causing it to pivot about the arm 28', of the U-shaped clip 28, to move the link forwardly to rotate the sear 26 on the pin 30 in a counterclockwise direction causing the sear shoulder 31 to drop beneath the bolt shoulder 32, as shown in Figure 4, permitting the bolt [0 to be moved forwardly by the driving springs If the trigger is held depressed, as shown in Figure 4, the bolt It will continue to reciprocate until the ammunition is exhausted. Short bursts or single shots, however, can be fired by releasin the trigger when desired in which case the .spring 27 will pivot the trigger 24 and the link 25 towards each other, as a result of which the link 25 will pivot the sear 26 in a clockwise direction until the step 29 abuts the arm 28" as shown in Figures 2 and 3. In this position, the shoulder sear 3! is projected into the path of the reciprocating bolt In which, as it moves backwards in recoil, will ride over the shoulder 3| cousing the sear 26 to rotate on the pin 30 to the position shown in Figure 4, forcing the link 25 to pivot away from the trigger 24 against the tension of the spring 2?.

As soon as the bolt shoulder 32 has been carried to the rear to clear the sear shoulder 3|, it will be raised into the path of the bolt shoulder 32 by the action of the spring 21, always tendin to maintain the trigger 24 and the link 25 pivoted towards each other. When the bolt [0 has completed its recoil movement and has commenced its forward movement preparatory for the next firing cycle, its shoulder 32 will strike the sear shoulder 3|, as shown in Figure 2 and be held against further forward movement in this cocked position until the trigger is operated again.

We claim:

1. In a firearm, the combination of a receiver having an opening in the bottom thereof, a bolt reciprocable in said receiver, and a subassembly comprising a trigger, a rotatable searincluding an integral step, a link pivoted to said trigger and said sear whereby rotation of the trigger rotates the sear in a first direction to release the bolt for forward movement, said link comprising a channel shaped member provided at each end thereof with a pair of longitudinally extending arms, one pair of said arms received within said trigger and the other pair of said arms straddling the said sear, spring means between said trigger and said link and a unitary means comprising a U-shaped clip one arm of said clip pivotally mounting said trigger in said receiver, the other arm of said clip cooperating with said step to limit rotation of said sear'in a second direction, said subassembly being insertable in and removable from said receiver through said opening as a unit.

2. In a firearm a subassembly comprising arotatable trigger having a free end, a link at the opposite end thereof pivotally secured to said trigger, a, sear having an integral step pivotally secured to the other end of said link whereby rotation of said trigger rotates said sear, a spring engaged between said trigger and said link resisting such rotation, one end of said spring engaging said trigger between the free end thereof and the center of rotation, a clip havingtwo laterally extending arms, one of said arms pivoting said trigger between the link and the spring, the other of said arms limiting the rotation of said sear by cooperation with said step, the said subassembly being insertable in and removable from the said firearm as a unit.

FREDERICK W. SAMPSON. GEORGE J. HYDE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 

